The invention relates to a two-for-one twisting spindle comprising a pneumatically actuated threading device and, more particularly, to such a twisting spindle comprising a spindle bolt that is rotatable about its vertically arranged rotational axis, wherein an injector opens into a thread guiding channel, the injector can be temporarily connected to a compressed air source by a compressed air supply and the thread is conveyed through the thread guiding channel by means of an air flow during the threading process.
In the case of two-for-one twisting spindles, the thread is generally drawn off upwardly from the stationary supply bobbin, introduced into the upper end of a thread inlet tube, deflected downwardly and guided to the spindle rotor which it leaves through a thread guiding channel or a thread outlet channel in the radial direction.
After leaving the thread guiding channel, the thread is guided upwardly and in the process forms a balloon rotating about the supply bobbin. A thread guiding eyelet is used as a balloon limiter. The thread then runs via a thread traversing guide and is wound on a take-up bobbin.
On modern two-for-one twisting machines, the thread is threaded by means of compressed air and a threading injector. For the threading process, compressed air is supplied to the threading injector so a vacuum is produced which sucks the thread through the hollow shaft of the spindle, and so the thread is then conveyed radially outwardly by means of an air flow through the thread guiding channel.
The threading injector is arranged, for example, on the stationary part of the hollow shaft, and the air supply is supplied horizontally through the protection pot of the two-for-one twisting spindle, as disclosed in European Patent Publication EP 0 489 225 B1. In a further embodiment shown in the generic German Patent Publication DE 30 12 427 C2, the injector is a component of the rotating storage disc. The air is supplied through the hollow shaft of the spindle bolt.
These embodiments have the drawback that a relatively large number of components have to be sealed and adapted with respect to one another. Expensive processing steps of the components, for example to form the air channels are necessary, in particular, for the air guidance.